Photocenter Shift Effect in Double Stars of Gaia DR2 Database

Abstract

In order to check the performance of the Gaia satellite when detecting double stars, we attempted to discover a photocenter shift affecting Gaia's second data release (Gaia DR2). We analyzed data of bona-fide double stars from "Double and Multiple System Annex" catalog and matched them with the Gaia DR2 catalog. We tried to derive a relationship between measurements of visual magnitude and signs of binarity based on parallaxes and proper motions. A comprehensive study of parallaxes indicates the presence of the photocenter shift effect. Due to the proper motion two-dimensional nature, we conducted only a simply study which implies that a real photocenter shift may affect double stars appearing in the Gaia DR2 catalog as single sources.